On-Demand Generation of an Efficient Catalyst for Pyridine Formation from Unactivated Nitriles and α,ω-Diynes Using CoCl₂-6H₂O, dppe, and Zn

Abstract

[reaction: see text] A highly practical, general method for catalytic formation of substituted pyridines from a variety of unactivated nitriles and alpha,omega-diynes is given. The reactions which were catalyzed by 5 mol % of dppe/CoCl2-6H2O in the presence of Zn powder (10 mol %) could proceed at rt to approximately 50 degrees C with high functional compatibility and regioselectivity.

Simple and Fast Synthesis of New Axially Chiral Bipyridine N,N′‐Dioxides for Highly Enantioselective Allylation of Aldehydes

“…Once again, as in our previous work, tetrayne 2 was chosen as a starting material. Attempts to selectively monocyclotrimerize 2 with benzonitrile using Okamoto conditions (CoCl 2 ·6 H 2 O, Zn, dppe, NMP or DMF) [17] were met only with partial success. Disappointingly, the reaction proceeded with low selectivity giving the expected 1-diynyltetrahydroisoquinoline 3 only in 10% isolated yield.…”

Diversity Synthesis of Complex Pyridines Yields a Probe of a Neurotrophic Signaling Pathway

“…(3) The CpCo(CO) 2 catalyzed reaction has been widely used in recent years. (4) These reactions typically require high temperature and irradiation to generate active Co(I) by liberating CO, limiting overall generality.…”

A Straightforward Procedure for the [2+2+2] Cycloaddition of Enediynes

“…[12,13] Diels-Alder, [14] homo-DielsAlder reactions, [15] and Alder-ene reactions, [16] [6 + 2], [17] reductive [3 + 2], [18] and [4 + 2 + 2] cycloadditions, [19] cyclizations of o-iodobenzoates with aldehydes, [20] aryl-sulfur bond formations, [21] Reformatsky reactions, [22] cross-couplings and conjugate additions [23] were also performed under these conditions. Therefore, common catalysts of type CpCoL 2 could be replaced by catalytic systems much easier to handle (and sometimes more efficient [11a] ) to generate benzenes or pyridines by [2 + 2 + 2] approaches.…”